Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $222.39   9.326%   $243.1301   $243.13   $243.15   $243.10  
  Purchase #2 $116.52   8.153%   $126.0199   $126.02   $126.00   $126.00  
  Purchase #3 $219.82   11.123%   $244.2706   $244.27   $244.25   $244.30  
  Purchase #4 $222.85   11.442%   $248.3485   $248.35   $248.35   $248.30  
  Purchase #5 $229.39   7.647%   $246.9315   $246.93   $246.95   $246.90  
  Purchase #6 $141.34   12.827%   $159.4697   $159.47   $159.45   $159.50  
  Purchase #7 $192.46   7.621%   $207.1274   $207.13   $207.15   $207.10  
  7 purchase totals = $1,344.77       $1,475.2977   $1,475.30   $1,475.30   $1,475.20